In a conventional perforated photographic film such as a 35 mm photographic film, perforations are provided at regular intervals in the vicinity of side edge portions of the film. For instance, in the 35 mm. film, the pitch of perforations is about 4,735 mm. Perforations are originally provided in a movie film with a view to transporting the film by bringing a sprocket of a movie projector into mesh engagement with them.
In addition, in a still camera, a sprocket is brought into mesh engagement with perforations so as to detect a film transporting amount to thereby control the film transporting amount for each frame, but in a reversal film, since the edge portion of a picture taken, for instance, with a dark background and a gap between pictures equally become dark when developed, when trying to sever the developed reversal film into frames, it is not easy to locate a boundary between the edge portion of the picture and a gap between pictures and a one adjacent to it. Moreover, since a gap is set to be located substantially at an intermediate position between perforations aligned at a small pitch in a direction in which a perforated roll film is transported, there is provided no target indicating a severing position, causing a risk of making a mistake in recognizing a severing position when trying to sever the film to thereby damage a picture. Thus, there is problem in which proper care should be exercised in handling the film.
Then, in order to facilitate the recognition of severing positions to thereby improve the handling properties of a developed film when trying to sever it into frames, the applicant of the present invention has proposed a photographic roll film in which a perforation is disposed at a gap portion between photographic areas or frames of the film, as well as a photographic film in which the perforation so disposed are formed into an oval which is made elongate in a direction in which the film is transported. In this photographic film, the pitch of the perforations so provided is set equal to that of a photographic area of a camera so that they serve as a target indicating a severing position of the photographic film when it is used in a camera in which its film transporting mechanism is designed so as to match the perforations which are situated at a gap portion between photographic areas or frames.
In addition, the applicant of the present invention purposes a slide mount desirable for mounting a photographic film configured as described above. In this slide mount, positioning pins are provided at four corners of a film table portion of a mount frame in such a manner as to upwardly protrude therefrom. The positioning pins are formed so as to have such an outside diameter that the perforations can be brought into engagement with them, and the vertical and longitudinal pitches are made equal to those of the perforations of the afore-mentioned photographic film. Therefore, when the photographic film severed into a frame is placed on the film table portion and then a film presser cover is fittingly mounted on the mount frame, the perforations at the four corners of the severed photographic film are brought into engagement with the positioning pins, the photographic film being thereby accurately positioned for mounting.
The risk of making a mistake in locating a cutting position when trying to sever a photographic film into frames can almost be eliminated by disposing perforations at gaps between photographic areas or frames of the film. In a case, however, where the width of the gap between photographic areas or frames is made as small as possible to reduce the loss of a photographic film, and if a cutting position is determined within the range of the longitudinal length of the perforation, a risk of cutting the film at the edge portion of a picture will arise. Thus, if a more accurate target is available as a cutting position, the handling of a film in cutting it will be easier.
Thus, there will arise a technical issue to be solved in order to facilitate the film cutting operation by accurately cutting a film at the longitudinally central position of the perforation, and an object of the present invention is to solve this issue.